Optical imaging system

ABSTRACT

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, disposed in order from an object side to an imaging plane. One or any combination of the first lens to the seventh lens are formed of glass. One or both surfaces of one or more of the first lens to the seventh lens are aspherical. A pair of lenses, among the first lens to the seventh lens, allows paraxial areas opposing each other to be bonded to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/060,427 filed on Oct. 1, 2020, now U.S. Pat. No. 11,474,330 issued onOct. 18, 2022, which is a continuation of U.S. patent application Ser.No. 16/218,648 filed on Dec. 13, 2018, now U.S. Pat. No. 10,830,997issued on Nov. 10, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/585,304 filed on May 3, 2017, now U.S. Pat. No.10,185,126 issued on Jan. 22, 2019, and claims the benefit under 35 USC119(a) of Korean Patent Application No. 10-2016-0164493 filed on Dec. 5,2016, in the Korean Intellectual Property Office, the entire disclosuresof which are incorporated herein by reference for all purposes.

BACKGROUND 1. Field

The following description relates to an optical imaging system includinglenses formed of a glass material.

2. Description of Related Art

Small surveillance cameras may be mounted on a vehicle to capture viewsto the front and rear of the vehicle. For example, a small surveillancecamera may be mounted on a rearview mirror of a vehicle to image movingvehicles, pedestrians, and other objects positioned to the front of thevehicle. A small surveillance camera is used for not only for thepurpose of capturing an image of a simple object, but also as a sensorfor recognizing the presence or absence of an object.

A surveillance camera used as a sensor requires high resolution, so asto detect fine movement. The resolution of a surveillance camera for asensor may be improved through an optical system having a high degree ofbrightness. However, an optical system having an extremely high degreeof brightness increases the camera's internal temperature, and thus, theresolution of surveillance camera may be limited. Therefore, thedevelopment of an optical imaging system to be used in such asurveillance camera for a sensor having high resolution and uniformresolution, even at a high temperature, is required.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, an optical imaging system includes a first lens,a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens,and a seventh lens, disposed from an object side and having refractivepower. One or any combination of the first lens to the seventh lens areformed of glass. One or both surfaces of one or more of the first lensto the seventh lens are aspherical. A pair of lenses, from among thefirst lens to the seventh lens, is disposed to allow paraxial areasopposing each other to be bonded to each other.

The optical imaging system can further include a stop disposed betweenthe fourth lens and the fifth lens. The first lens to the seventh lensof the optical imaging system may each be formed of glass. One or bothsurfaces of the seventh lens can be aspherical in the optical imagingsystem.

The optical imaging system can include an image-side surface of thefifth lens bonded to an object-side surface of the sixth lens. The firstlens and the second lens of the optical imaging system can have ameniscus shape in which image-side surfaces of the first lens and thesecond lens are concave. The optical imaging system may also includeopposing surfaces of the third lens and the fourth lens, which areconvex along an optical axis.

The optical imaging system can include the fifth lens having a conveximage-side surface along an optical axis. The optical imaging system mayinclude the sixth lens having a concave object-side surface along anoptical axis. The optical imaging system can include convex surfacesalong an optical axis for both surfaces of the seventh lens.

In another general aspect, an optical imaging system includes a firstlens having a negative refractive power, a second lens having a negativerefractive power, a third lens having a negative refractive power, and afourth lens having a positive refractive power. The optical imagingsystem includes a fifth lens having a positive refractive power, a sixthlens having a negative refractive power, and a seventh lens having apositive refractive power. The first lens to the seventh lens aresequentially disposed from an object side to an imaging plane. One orany combination of the first lens to the seventh lens are formed ofglass.

One or both surfaces of the seventh lens can be aspherical in theoptical imaging system. The third lens of the optical imaging system mayinclude a concave object-side surface along an optical axis. The fourthlens of the optical imaging system may have a convex object-side surfacealong an optical axis. Both surfaces of the fifth lens can be convexalong an optical axis. Both surfaces of the sixth lens of the opticalimaging system may be concave along an optical axis.

In another general aspect, an optical imaging system includes a firstlens having a convex object-side surface along an optical axis; a secondlens having a convex object-side surface along the optical axis; and athird lens having a convex image-side surface along the optical axis.The optical imaging system also includes a fourth lens, a fifth lens, asixth lens, and a seventh lens. The first lens to the seventh lens aresequentially disposed from an object side to an imaging plane. One orany combination of the first lens to the seventh lens are formed ofglass.

Each of the first lens to the seventh lens may be formed of glass in theoptical imaging system. The fourth lens, the fifth lens and the seventhlens of the optical imaging system can each have a positive refractivepower. The optical imaging system may have an angle of view that is 150°or more.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view of an optical imaging system according to a firstexample.

FIGS. 2 and 3 illustrate modulation transfer function (MTF) curvesaccording to a change in a temperature of the optical imaging systemillustrated in FIG. 1 .

FIG. 4 is a view of an optical imaging system according to a secondexample.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements, where applicable. The drawings maynot be to scale, and the relative size, proportions, and depiction ofelements in the drawings may be exaggerated for clarity, illustration,and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of functions and constructions that are well known in theart may be omitted for increased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various components, regions, or sections, these components,regions, or sections are not to be limited by these terms. Rather, theseterms are only used to distinguish one component, region, or sectionfrom another component, region, or section. Thus, a first component,region, or section referred to in examples described herein may also bereferred to as a second component, region, or section without departingfrom the teachings of the examples.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

In the present specification, all radii of curvature of lenses,thicknesses, and focal lengths of each lens are indicated in millimeters(mm). A person skilled in the relevant art will appreciate that otherunits of measurement may be used. Further, in embodiments, all radii ofcurvature, thicknesses, OALs (optical axis distances from the firstsurface of the first lens to the image sensor), a distance on theoptical axis between the stop and the image sensor (SLs), image heights(IMGHs) (image heights), and back focus lengths (BFLs) of the lenses, anoverall focal length of an optical system, and a focal length of eachlens are indicated in millimeters (mm). Further, thicknesses of lenses,gaps between the lenses, OALs, TLs, SLs are distances measured based onan optical axis of the lenses.

A surface of a lens being convex means that an optical axis portion of acorresponding surface is convex, and a surface of a lens being concavemeans that an optical axis portion of a corresponding surface isconcave. Therefore, in a configuration in which one surface of a lens isdescribed as being convex, an edge portion of the lens may be concave.Likewise, in a configuration in which one surface of a lens is describedas being concave, an edge portion of the lens may be convex. In otherwords, a paraxial region of a lens may be convex, while the remainingportion of the lens outside the paraxial region is either convex,concave, or flat. Further, a paraxial region of a lens may be concave,while the remaining portion of the lens outside the paraxial region iseither convex, concave, or flat. In addition, in an embodiment,thicknesses and radii of curvatures of lenses are measured in relationto optical axes of the corresponding lenses.

In accordance with illustrative examples, the embodiments described ofthe optical system include seven lenses with a refractive power.However, the number of lenses in the optical system may vary, forexample, between two to seven lenses, while achieving the variousresults and benefits described below. Also, although each lens isdescribed with a particular refractive power, a different refractivepower for at least one of the lenses may be used to achieve the intendedresult.

Examples provide an optical imaging system having uniform resolutioneven in a high temperature environment. Hereinafter, examples aredescribed in further detail with reference to the accompanying drawings.An optical imaging system includes lenses. For example, the opticalimaging system includes seven lenses. Next, configurations of respectivelenses noted above will be described.

A first lens has a refractive power. For example, the first lens has anegative refractive power. One surface of the first lens is convex. Inan embodiment, an object-side surface of the first lens is convex.

The first lens has a spherical surface. For example, both surfaces ofthe first lens are spherical. The first lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.In an example, the first lens is formed of a glass material. However, amaterial of the first lens is not limited to being glass. In anotherexample, the first lens may be formed of a plastic material.

The first lens has a refractive index. For example, the refractive indexof the first lens is 1.70 or more. The first lens has an Abbe numberlower than that of a second lens. In an embodiment, an Abbe number ofthe first lens may be 50 or less.

A second lens has a refractive power. For example, the second lens has anegative refractive power. One surface of the second lens is convex. Inan embodiment, an object-side surface of the second lens is convex.

The second lens has a spherical surface. For example, both surfaces ofthe second lens are spherical. The second lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.In an example, the second lens is formed of a glass material. However, amaterial of the second lens is not limited to being glass. In anotherexample, the second lens may be formed of a plastic material.

The second lens has a refractive index. For example, the refractiveindex of the second lens is 1.550 or less. The second lens has an Abbenumber higher than that of the first lens. In an embodiment, an Abbenumber of the second lens is 60 or more.

A third lens has a refractive power. For example, the third lens has anegative refractive power. One surface of the third lens is convex. Inan embodiment, an image-side surface of the third lens is convex.

The third lens has a spherical surface. For example, both surfaces ofthe third lens are spherical. The third lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.In an example, the third lens is formed of a glass material. However, amaterial of the third lens is not limited to being glass. In anotherexample, the third lens may be formed of a plastic material.

The third lens has a refractive index. For example, the refractive indexof the third lens is 1.80 or more. The third lens has an Abbe numberlower than that of the second lens. In an embodiment, an Abbe number ofthe third lens is 50 or less.

A fourth lens has a refractive power. For example, the fourth lens has apositive refractive power. One surface of the fourth lens is convex. Inan embodiment, an object-side surface of the fourth lens is convex.

The fourth lens has a spherical surface. For example, both surfaces ofthe fourth lens are spherical. The fourth lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.In an example, the fourth lens is formed of a glass material. However, amaterial of the fourth lens is not limited to being glass. In anotherexample, the fourth lens may be formed of a plastic material.

The fourth lens has a refractive index. For example, the refractiveindex of the fourth lens is 1.70 or more. The fourth lens has an Abbenumber lower than those of its adjacent lenses (that is, the third lensand the fifth lens). In an embodiment, an Abbe number of the fourth lensis 40 or less.

A fifth lens has a refractive power. For example, the fifth lens has apositive refractive power. One surface of the fifth lens is convex. Inan embodiment, an image-side surface of the fifth lens is convex.

The fifth lens has a spherical surface. For example, both surfaces ofthe fifth lens are spherical. The fifth lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.In an example, the fifth lens is formed of a glass material. However, amaterial of the fifth lens is not limited to being glass. In anotherexample, the fifth lens may be formed of a plastic material.

The fifth lens has a refractive index. For example, the refractive indexof the fifth lens is 1.70 or less. The fifth lens has an Abbe numberhigher than those of its adjacent lenses (that is, the fourth lens andthe sixth lens). In an embodiment, an Abbe number of the fifth lens is50 or more.

A sixth lens has a refractive power. For example, the sixth lens has anegative refractive power. One surface of the sixth lens is concave. Inan embodiment, an object-side surface of the sixth lens is concave.

The sixth lens has a spherical surface. For example, both surfaces ofthe sixth lens are spherical. The sixth lens is formed of a materialhaving a high degree of light transmissivity and excellent workability.In an example, the sixth lens is formed of a glass material. However, amaterial of the sixth lens is not limited to being glass. In anotherexample, the sixth lens may be formed of a plastic material.

The sixth lens has a refractive index. For example, the refractive indexof the sixth lens is 1.80 or more. The sixth lens may have an Abbenumber lower than those of its adjacent lenses (that is, the fifth lensand the seventh lens). In an embodiment, an Abbe number of the sixthlens is 30 or less.

A seventh lens has a refractive power. For example, the seventh lens hasa positive refractive power. One surface of the seventh lens is convex.In an embodiment, an object-side surface of the seventh lens is convex.

The seventh lens has an aspherical surface. For example, both surfacesof the seventh lens are aspherical. The seventh lens is formed of amaterial having a high degree of light transmissivity and excellentworkability. In an example, the seventh lens is formed of a glassmaterial. However, a material of the seventh lens is not limited tobeing glass. In another example, the seventh lens may be formed of aplastic material.

The seventh lens has a refractive index. For example, the refractiveindex of the seventh lens is 1.60 or more. The seventh lens has an Abbenumber higher than that of the sixth lens. In an embodiment, an Abbenumber of the seventh lens is 60 or more.

An optical imaging system has one or more aspheric lenses. For example,one or more of the first lens to the seventh lens may have an asphericalsurface. As described above, the optical imaging system including one ormore aspheric lenses is advantageous for implementing high resolution.For reference, an aspherical surface may be represented by Equation 1below.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar^{4}} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr^{16}} + {Hr^{18}}}} & (1)\end{matrix}$

In Equation 1, c represents an inverse of a radius of curvature of thelens, k represents a conic constant, r represents a distance from acertain point on an aspherical surface of the lens to an optical axis, Ato H represent aspherical constants, and Z (or SAG) represents adistance between the certain point on the aspherical surface of the lensat the distance r and a tangential plane meeting the apex of theaspherical surface of the lens.

The optical imaging system includes an image sensor. The image sensor isconfigured to provide high resolution. A surface of the image sensorforms an imaging plane on which an image is focused.

The optical imaging system includes a stop. The stop is disposed betweentwo lenses. For example, the stop may be disposed between the fourthlens and the fifth lens. The stop disposed described above adjusts anamount of light incident on the image sensor.

The stop is configured to divide refractive power of the optical imagingsystem into two parts. For example, total refractive power of lenseslocated in the front (an object side) of the stop is negative, and totalrefractive power of lenses located in the back (an imaging plane side)of the stop is positive. Such an arrangement may be advantageous inreducing an overall length of an optical system while widening an angleof view of an optical imaging system.

The optical imaging system includes a filter. The filter is disposedbetween the seventh lens and the image sensor to remove a componentlimiting resolution. For example, the filter may block infraredwavelengths of light. The filter has a refractive index. For example,the refractive index of the filter may be 1.50 or more. The filter hasan Abbe number substantially similar to that of the seventh lens. Forexample, an Abbe number of the filter is 60 or more.

The optical imaging system is configured to significantly reduce achange in a focal length due to a temperature. For example, in theoptical imaging system, the fourth lens, the fifth lens, and the seventhlens, having positive refractive power, may have weak refractive powerof 3 or more.

The optical imaging system configured as described above has uniformresolution even at a high temperature and a low temperature. Thus, evenwhen the optical imaging system is installed in a place easily exposedto an external environment such as a front bumper and a rear bumper of avehicle, a clear image may be provided for a user.

In addition, the optical imaging system configured as described abovehas a wide angle of view of 150 degrees or more. Thus, the opticalimaging system may not only be applied to a surveillance camera of avehicle, but also to a camera requiring a wide angle of view, such as asurveillance camera for a drone.

Next, an optical imaging system, according to an example, will bedescribed. First, a shape of an optical imaging system, according to anexample, will be described with reference to FIG. 1 . An optical imagingsystem 100 includes lenses having respective refractive powers. Forexample, optical imaging system 100 includes a first lens 110, a secondlens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixthlens 160, and a seventh lens 170.

In the first example, the first lens 110 has a negative refractivepower. An object-side surface of lens 110 is convex and an image-sidesurface of lens 110 is concave. The second lens 120 has a negativerefractive power. An object-side surface of lens 120 is convex and animage-side surface of lens 120 is concave. The third lens 130 has anegative refractive power. An object-side surface of lens 130 is concaveand an image-side surface of lens 130 is convex. The fourth lens 140 hasa positive refractive power. An object-side surface of lens 140 isconvex and an image-side surface of lens 140 is concave.

The fifth lens 150 has a positive refractive power. Both surfaces oflens 150 are convex. The sixth lens 160 has a negative refractive power.Both surfaces of lens 160 are concave. The seventh lens 170 has apositive refractive power. Both surfaces of lens 170 are convex.

Optical imaging system 100 includes a stop ST. Stop ST is disposedbetween fourth lens 140 and fifth lens 150. Stop ST disposed asdescribed above blocks peripheral light causing lateral aberration(coma), astigmatism, rectilinear distortion, and lateral chromaticaberration to improve resolution of optical imaging system 100.

Optical imaging system 100 includes a filter 180. Filter 180 is disposedbetween seventh lens 170 and an imaging plane 190. Filter 180 blocksinfrared light, and prevents foreign objects from penetrating into animaging plane.

Optical imaging system 100 includes an image sensor. The image sensorforms imaging plane 190 in which light refracted through a lens allowsan image to be formed.

Optical imaging system 100 includes cemented lenses. For example, fifthlens 150 and sixth lens 160 are disposed in a configuration to be bondedto each other in optical imaging system 100. A cemented surface of fifthlens 150 and sixth lens 160 is convex toward an image. For example, animage-side surface of the fifth lens 150 may be convex, and anobject-side surface of the sixth lens 160 may be concave.

Optical imaging system 100 has a wide angle of view. For example,optical imaging system 100 has an angle of view of 195 degrees. Opticalimaging system 100 has a low F number. For example, an F number ofoptical imaging system 100 is 2.0. For reference, an overall focallength of optical imaging system 100 is 1.9.

With reference to FIGS. 2 and 3 , modulation transfer function (MTF)characteristics of the optical imaging system in a high or lowtemperature environment will be described. For reference, FIG. 2 is agraph illustrating MTF values of optical imaging system 100, measured inan environment of 85 degrees above zero. FIG. 3 is a graph illustratingMTF values of optical imaging system 100 measured in an environment of40 degrees below zero.

Optical imaging system 100, according to the first example, has uniformresolution even at a high temperature or at a low temperature. Forexample, optical imaging system 100 may implement characteristics inwhich an MTF value is substantially uniform from 0 degree to 94 degrees,which is a center of an optical axis. These characteristics areimplemented even in a high-temperature environment of 80 degrees abovezero or more, as illustrated in FIG. 2 . Similarly, optical imagingsystem 100 may implement characteristics in which an MTF value issubstantially uniform from 0 degree to 98 degrees, which is a center ofan optical axis. Again, these characteristics are implemented even in alow-temperature environment of 40 degrees below zero, as illustrated inFIG. 3 .

Therefore, the optical imaging system 100, according to the firstexample, is applied to a camera frequently exposed externally or usuallyexposed externally to obtain a high-resolution image. As describedabove, lens characteristics and aspherical characteristics of opticalimaging system 100, according to the first example, are listed in Tables1 and 2 below. The asterisks next to surface numbers S14 and S15 inTable 1 indicate that these surfaces are aspherical.

TABLE 1 First Example Surface Radius of Thickness/ Refractive AbbeEffective Focal Number Element Curvature Distance Index Number RadiusLength S0 Infinity S1 First 11.0000 0.7000 1.772 49.6 5.30 −5.555 S2Lens 3.0000 1.9100 2.84 S3 Second 14.9600 0.5000 1.516 64.2 2.69 −7.353S4 Lens 2.9920 1.4030 1.95 S5 Third −3.5000 2.2010 1.804 46.5 1.95−79.649 S6 Lens −4.7400 0.1000 2.20 S7 Fourth 5.5000 2.0000 1.749 35.01.99 7.959 S8 Lens 60.0000 0.5430 1.52 S9 Stop Infinity 1.3520 1.30 S10Fifth 5.1070 2.5000 1.612 58.6 2.14 3.497 S11 Lens −3.0000 0.0000 2.14S12 Sixth −3.0000 1.3000 1.805 25.4 2.21 −2.933 S13 Lens 13.2220 0.18702.64 S14* Seventh 4.3580 2.4490 1.618 63.8 3.01 4.419 S15* Lens −5.74501.0000 3.20 S16 Filter Infinity 0.8000 1.516 64.2 3.11 S17 Infinity1.0300 3.09 S18 Imaging Infinity 3.03 Plane

TABLE 2 Aspherical Constant S14 S15 K −2.1298390 −1.2602675 A −0.00342310.0007732 B 0.0003008 0.0000472 C −0.0000179 0.0000017 D −0.0000005−0.0000011 E −2.1298390 −1.2602675 F 0.0000000 0.0000000 G 0.00000000.0000000 H 0.0000000 0.0000000

Next, with reference to FIG. 4 , a shape of an optical imaging systemaccording to another example will be described. An optical imagingsystem 200 includes lenses having respective refractive powers. Forexample, the optical imaging system 200 includes a first lens 210, asecond lens 220, a third lens 230, a fourth lens 240, a fifth lens 250,a sixth lens 260, and a seventh lens 270.

In an example, the first lens 210 has a negative refractive power. Anobject-side surface of lens 210 is convex and an image-side surface oflens 210 is concave. The second lens 220 has a negative refractivepower. An object-side surface of lens 220 is convex and an image-sidesurface of lens 220 is concave. The third lens 230 has a negativerefractive power. An object-side surface of lens 230 is concave and animage-side surface of lens 230 is convex.

The fourth lens 240 has a positive refractive power. Both surfaces oflens 240 are convex. The fifth lens 250 has a positive refractive power.Both surfaces of lens 250 are convex. The sixth lens 260 has a negativerefractive power. Both surfaces of lens 260 are concave. The seventhlens 270 has a positive refractive power. Both surfaces of lens 270 areconvex.

Optical imaging system 200 includes a stop ST. Stop ST is disposedbetween fourth lens 240 and fifth lens 250. Stop ST disposed asdescribed above blocks peripheral light causing lateral aberration(coma), astigmatism, rectilinear distortion, and lateral chromaticaberration to improve resolution of optical imaging system 200.

Optical imaging system 200 includes a filter 280. Filter 280 is disposedbetween the seventh lens 270 and an imaging plane 290. Filter 280 blocksinfrared light and prevents foreign objects from penetrating into animaging plane.

Optical imaging system 200 includes an image sensor. The image sensorforms imaging plane 290, in which light refracted through a lens allowsan image to be formed.

Optical imaging system 200 includes cemented lenses. For example, fifthlens 250 and sixth lens 260 are disposed in a configuration to be bondedto each other in optical imaging system 200. A cemented surface of fifthlens 250 and sixth lens 260 is convex toward an image. For example, animage-side surface of fifth lens 250 may be convex, and an object-sidesurface of sixth lens 260 may be concave.

Optical imaging system 200 has a wide angle of view. For example,optical imaging system 200 has an angle of view of 150 degrees. Opticalimaging system 200 has a low F number. For example, an F number ofoptical imaging system 200 is 2.05. For reference, an overall focallength of the optical imaging system 200 is 1.85. As described above,lens characteristics and aspherical characteristics of optical imagingsystem 200, according to the second example, are listed in Tables 3 and4 below. The asterisks next to surface numbers S14 and S15 in Table 3indicate that these surfaces are aspherical.

TABLE 3 Second Example Surface Radius of Thickness/ Refractive AbbeEffective Focal Number Element Curvature Distance Index Number RadiusLength S0 Infinity S1 First 13.0000 0.7000 1.772 49.6 5.20 −5.915 S2Lens 3.3000 1.7600 2.98 S3 Second 14.9600 0.4900 1.516 64.2 2.81 −7.344S4 Lens 2.9900 1.8500 2.18 S5 Third −5.1700 2.5300 1.804 46.5 2.03−24.734 S6 Lens −8.5100 0.1500 2.15 S7 Fourth 6.0300 2.1000 1.749 35.02.06 6.406 S8 Lens −19.9900 0.6300 1.68 S9 Stop Infinity 1.2400 1.35 S10Fifth 4.5100 2.2000 1.612 58.6 2.05 3.312 S11 Lens −3.0000 0.0000 2.05S12 Sixth −3.0000 0.5000 1.805 25.4 2.07 −2.725 S13 Lens 8.7700 0.70002.26 S14* Seventh 4.7600 2.2200 1.618 63.8 2.72 4.731 S15* Lens −6.23001.0000 2.90 S16 Filter Infinity 0.8000 1.516 64.2 2.98 S17 Infinity1.0700 3.00 S18 Imaging Infinity 0.0080 3.11 Plane

TABLE 4 Aspherical Constant S14 S15 K −3.814743 −29.576662 A −0.003692−0.013405 B 0.000836 0.002777 C −0.000229 −0.000390 D 0.000017 0.000021E −3.814743 −29.576662 F 0.000000 0.000000 G 0.000000 0.000000 H0.000000 0.000000

As set forth above, according to examples, an optical imaging system hasuniform resolution regardless of changes in temperature. While thisdisclosure includes specific examples, it will be apparent after anunderstanding of the disclosure of this application that various changesin form and details may be made in these examples without departing fromthe spirit and scope of the claims and their equivalents. The examplesdescribed herein are to be considered in a descriptive sense only, andnot for purposes of limitation.

Descriptions of features or aspects in each example are to be consideredas being applicable to similar features or aspects in other examples.Suitable results may be achieved if the described techniques areperformed in a different order, and/or if components in a describedsystem, architecture, device, or circuit are combined in a differentmanner, and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system comprising: a firstlens having a convex object-side surface in a paraxial region thereof; asecond lens having a negative refractive power and a convex object-sidesurface in a paraxial region thereof; a third lens having a refractivepower; a fourth lens having a concave image-side surface in a paraxialregion thereof and a convex object-side surface in a paraxial regionthereof; a fifth lens having a refractive power; a sixth lens having aconcave image-side surface in a paraxial region thereof; and a seventhlens having a refractive power, wherein the first to seventh lenses aresequentially disposed in ascending numerical order along an optical axisof the optical imaging system from an object side of the optical imagingsystem toward an imaging plane of the optical imaging system, wherein aradius of curvature of an image-side of the fifth lens is greater than aradius of curvature of an image side surface of the third lens, whereina radius of curvature of the image-side surface of the fourth lens isgreater than a radius of curvature of the object-side surface of thefirst lens, and wherein the optical imaging system has a total number ofseven lenses having a refractive power.
 2. The optical imaging system ofclaim 1, wherein the third lens has a negative refractive power.
 3. Theoptical imaging system of claim 1, wherein the third lens has a conveximage-side surface in a paraxial region thereof.
 4. The optical imagingsystem of claim 1, wherein the fifth lens has a convex object-sidesurface in a paraxial region thereof.
 5. The optical imaging system ofclaim 1, wherein the seventh lens has a convex object-side surface in aparaxial region thereof.
 6. The optical imaging system of claim 1,wherein an Abbe number of the fourth lens is 40 or less.
 7. An opticalimaging system comprising: a first lens having a convex object-sidesurface in a paraxial region thereof; a second lens having a negativerefractive power and a convex object-side surface in a paraxial regionthereof; a third lens having a refractive power; a fourth lens having arefractive power; a fifth lens having a refractive power; a sixth lenshaving a concave image-side surface in a paraxial region thereof; and aseventh lens having a refractive power, wherein: the first to seventhlenses are sequentially disposed in ascending numerical order along anoptical axis of the optical imaging system from an object side of theoptical imaging system toward an imaging plane of the optical imagingsystem, the optical imaging system has a total number of seven lenseshaving a refractive power, an Abbe number of the fourth lens is 40 orless, a radius of curvature of an image-side surface of the fifth lensis greater than a radius of curvature of an image-side surface of thethird lens, and a radius of curvature of an image-side surface of thefourth lens is greater than a radius of curvature of the object-sidesurface of the first lens.
 8. The optical imaging system of claim 7,wherein the third lens has a negative refractive power.
 9. The opticalimaging system of claim 8, wherein the fourth lens has a positiverefractive power.
 10. The optical imaging system of claim 7, wherein thethird lens has a convex image-side surface in a paraxial region thereof.11. The optical imaging system of claim 7, wherein the fourth lens has aconvex object-side surface in a paraxial region thereof.
 12. The opticalimaging system of claim 7, wherein the fifth lens has a convexobject-side surface in a paraxial region thereof.
 13. The opticalimaging system of claim 7, wherein a distance along the optical axisfrom an image-side surface of the fourth lens to an object-side surfaceof the fifth lens is greater than a distance along the optical axis froman image-side surface of the second lens to an object-side surface ofthe third lens.
 14. An optical imaging system comprising: a first lenshaving a convex object-side surface in a paraxial region thereof; asecond lens having a negative refractive power and a convex object-sidesurface in a paraxial region thereof; a third lens having a negativerefractive power; a fourth lens having a concave image-side surface in aparaxial region thereof and a convex object-side surface in a paraxialregion thereof; a fifth lens having a refractive power; a sixth lenshaving a concave image-side surface in a paraxial region thereof; and aseventh lens having a refractive power, wherein the first to seventhlenses are sequentially disposed in ascending numerical order along anoptical axis of the optical imaging system from an object side of theoptical imaging system toward an imaging plane of the optical imagingsystem, wherein a radius of curvature of an image-side of the fifth lensis greater than a radius of curvature of an image side surface of thethird lens, and wherein the optical imaging system has a total number ofseven lenses having a refractive power.